1. Field of the Invention
This invention relates to compound valve devices in general, and more particularly to compound valve device for use in an exhaust gas control system for internal combustion engines.
2. Description of the Prior Art
In generally, an exhaust gas purification system, in case of controlling the pressures of various utilization means, needs as many valve devices as the various utilization means. As a result, the above system always includes undesirable problems which are complicated in system and high in cost. In order to solve the above problems, a compound valve device which operates two valve means in response to one signal pressure has been proposed. However, since a conventional valve device of this type has construction wherein two valve means are positioned axially, there is a drawback in that the operation of the two valve means have a difference in time in the opening and closing operation of the two valve means. Accordingly, when the conventional valve device is applied for use in an exhaust gas purification system of the internal combustion engine and so on, the system is not controlled surely and reliability in operation is reduced.